Fix IDs for Llama3 models

[kwadkore]

The Llama IDs for OpenRouter are prefixed by "meta-llama" instead of just "meta". Fix the ID so that they can be used successfully.

Motivation and Context

Attempting to use the models as implemented fails. OpenRouter returns with an error of the form: {"error":{"message":"meta/llama-3-70b is not a valid model ID","code":400}, ...}

Breaking Changes

No

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Type of the changes

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Tests improvement
• Refactoring

Checklist

• The pull request has a description of the proposed change
• I read the Contributing Guidelines before opening the pull request
• The pull request uses develop as the base branch
• Tests for the changes have been added
• All new and existing tests passed

Additional steps for pull requests adding a new feature

• An issue describing the proposed change exists
• The pull request includes a link to the issue
• The change was discussed and approved in the issue
• Docs have been added / updated